1. Field of the Invention
The present invention relates to a cleaning device for an inkjet printing head and a method for cleaning such a head. The present invention also relates to a wiper to be used for cleaning the inkjet recording head, and an inkjet recording apparatus having such a wiper.
2. Description of the Related Art
Printing apparatuses have their respective functions of printing, copying, and facsimile machines, or used as output devices of complex electronic devices (e.g., computers and word processors) and workstations. Each of such printing apparatuses is configured to print an image on an object to be printed (hereinafter, referred as a printing medium) such as a sheet of paper or a plastic sheet in accordance with image information. In addition, the printing apparatus may be classified into one of several types, i.e., inkjet type, wire-dot type, thermal type, laser-beam type, and the like by its printing procedure.
For a serial-type printing apparatus, a printing means performs a main-scanning movement in the direction (i.e., a main-scanning direction) that intersects the direction (i.e., a sub-scanning direction) of transferring a printing medium. The serial-type printing apparatus prints information throughout the printing medium by repeating the following procedure. First, the printing medium is arranged in a predetermined printing position, and subsequently one line of image is printed on the printing medium by the printing means mounted on a carriage that moves along the printing medium in the main-scanning direction. After that, the printing medium shifts its position at a predetermined pitch in the sub-scanning direction (i.e., a pitch transfer) and then a subsequent line of image is printed on the printing medium being stopped again.
For a line-type printing apparatus, on the other hand, a printing means does not perform a main-scanning movement and an image can be printed by a sub-scanning movement of printing medium in its transfer direction. The line-type printing apparatus prints information throughout the printing medium by repeating the following procedure. First, the printing medium is arranged in a predetermined printing position. Then, the printing means placed in a predetermined position prints one line of image on the printing medium at a time. Subsequently, the printing medium shifts its position at a predetermined pitch in the sub-scanning direction (i.e., a pitch transfer), followed by printing a subsequent line of image on the printing medium at a time.
Among the printing apparatuses, the inkjet type printing apparatus (also simply referred as an inkjet printing apparatus) prints information on a printing medium by ejecting ink thereon from a printing means (i.e., a printing head). Such an inkjet printing apparatus can be configured so as to easily make the printing means as compact as possible and print an image with extraordinary definition at high speed on a piece of ordinary paper without a specific treatment thereon. In addition, the inkjet printing apparatus has the advantages of: its excellent cost/performance ratio, an operation mode with a low noise level (i.e., a non-impact operation mode), and a multi-color print using multiple colors with ease. A line-type inkjet printing apparatus, in particular, uses a line-type-printing head where a plurality of orifices is arranged in the width direction of printing medium and allows a high-speed printing more than ever.
Particularly, an inkjet printing head that ejects ink using thermal energies can be easily made as one having a high-density liquid path arrangement (a high-density orifice arrangement) by means of semiconductor fabrication process including etching, sputtering, and deposition to form electrothermal conversion elements, electrodes, liquid-path walls, and a top plate on a substrate, resulting in compact more than ever.
There is a wide variety of demands on the material of printing medium. In recent years, the use of thin paper and converted paper (e.g., paper punched with holes or perforated for filing, and paper with some specified shape) has come to be demanded by a person skilled in the art in addition to the use of ordinary printing media such as ordinary paper and resin thin plate (e.g., OHP sheet).
For the inkjet printing apparatus described above, an ink-supplying path from an ink tank to the inkjet printing head may be contaminated with foreign substances such as dust and air bubbles. As an inner diameter of a liquid path communicating with an orifice formed on the printing head is small on the order of a few tens of micrometer, there is the fear of preventing a flow of ink passing through the liquid path by the depositing of the foreign substances on the interior wall of the liquid path when such substances arrive in the liquid path, resulting in the decreased efficiency of ink ejection and the decreased responsivity of ink ejection to printing signal. If such conditions become serious, ejection failures including a failed ink ejection may be caused as a result of clogging the orifice. The consistency of ink composition becomes increased when the ink ejection has not been performed even though ink remains in the liquid path of the inkjet printing apparatus. As a result, the ejection failures may be also caused by fixing the ink components on the liquid path.
There is also the possibility of the depositing of ink droplets, waterdrops, and foreign substance such as dust on a surface (also referred as an orifice surface) of ink-ejecting orifices of the inkjet printing head. Such a deposit may pull an ejected ink droplet to change the direction of ink ejection. As a result, an image degradation may be occurred.
For the sake of resolving those disadvantages, the inkjet printing apparatus has a specific configuration that cannot be found in other printing apparatuses. That is, an ejection-failure recovering system having means for cleaning ink in the liquid path and means for keeping the favorable condition of the orifice surface is provided on the inkjet printing apparatus.
Approaches for recovering the ejection failure by such a recovering system includes the introduction of fresh ink into the liquid path. For the introduction of fresh ink, there is a method known as xe2x80x9ca preliminary ejectionxe2x80x9d or xe2x80x9can empty ejectionxe2x80x9d, where ink which is not responsible for printing an image is ejected from the printing head into a predetermined ink receiver by driving an element that ejects energy for ejecting ink (an ejection energy generating element). Alternatively, there is another method known as xe2x80x9ca pumpingxe2x80x9d, where ink is forced to be discharged from an orifice by applying a predetermined pressure on the liquid path or by drawing in ink from the orifice by suction or the like.
Furthermore, there is a method known as xe2x80x9ca wipingxe2x80x9d using a wiping member that moves over an orifice surface of the inkjet printing head while maintaining continuous contact. In the wiping method, the orifice surface can be wiped clean of an ink droplet or a foreign substance (e.g., dust) being deposited in the vicinity of the orifice by relatively moving the printing head and the cleaning member.
For the wiping member, an elastic material such as urethane rubber is generally used. The performance of the wiping member depends on the quality of its material and the mechanical set-up condition. For maintaining the performance all the time, it is preferable to keep a surface of the wiping member clean. Thus, most of the inkjet printing apparatuses has a cleaning mechanism in which the wiping member wipes or scratches viscous ink or foreign substances and then pushes them to an absorber or the like so as to absorb the wiped or scratched one into the absorber.
If the ink being collected by the wiping member turns into the side of the printing head, the following problems may be caused. That is, for example, the accumulation of such viscous ink adheres on a pitch roller portion (a transfer means for a printing medium) and smears on the printing medium fed in place; the ink makes user""s hands or the exterior of a printing head dirty during the replacement of heads or the insertion and withdrawal thereof from a carriage; or the ink makes an electrical contact surface of the printing head dirty to prevent the continuity in signal line, resulting in the adverse effect on the motion of the printing apparatus.
Hereinafter, we will describe several methods of cleaning a printing head of a printing apparatus in a concrete manner as prior art examples.
A method known as an ejection failure-recovery mechanism by suction (hereinafter, referred as xe2x80x9ca recovery by suctionxe2x80x9d) includes the steps of capping a nozzle portion (i.e., a portion of ejecting ink) of the printing head by an elastic member (i.e., a capping member) and then making the inside pressure of the cap negative to recover the clogging of the above nozzle portion by removing undesired materials such as debris and viscous ink therefrom. Another method known as an ejection failure-recovery mechanism by applying pressure to each of the nozzles to force the undesired materials out of the nozzle portion (hereinafter, referred as xe2x80x9ca recovery by pressurizationxe2x80x9d). Following the recovery by suction or the recovery by pressurization, furthermore, there is a method of wiping an ink droplet by pressing an elastic member against the face (i.e., a surface where ink-ejecting orifices are formed) of the printing head to entirely remove the ink droplet being remained on the face (hereinafter, referred as xe2x80x9ca wipingxe2x80x9d). The wiping operation may be automatically performed after the expiration of a predetermined time interval to prevent the problem of a deposition of fine spray of ink or the like emitted from the nozzles on the face of the printing head (i.e., the nozzle portion is covered with the accumulated ink mist, resulting in an ink-ejection failure).
In ordinary cases, a wiping means to be used in the wiping operation described above is an elastic member formed as a sheet of rubber. The elastic member wipes the surface of the printing head in the direction perpendicular or parallel to a row of ink nozzles (i.e., ink-ejecting orifices) in accordance with the form of the printing head. Furthermore, there is another elastic member having its narrowed or broaden width with respect to that of the face of the printing head.
In the above wiping means, however, there is the fear of the laying-up of viscous ink on a surface of the wiping member as a result of increasing the viscosity of ink being adhered on that surface when the printing apparatus keeps on printing (i.e., character recording or the like) over an extended time period. If the wiping member is narrower than the face of the printing head, there is the fear of the deposition of ink on a portion of the face where the wiping member does not contact with. In this case, a sheet of printing paper may be smudged as a result of rubbing the paper with the printing head by the paper""s movement. If the wiping member is broader than the face of the printing head, there is the fear of the deposition of viscous ink on the edge portion of the face. When the ink is more deposited on the face, a pinch roller may receive any excess amount of the deposited ink. Thus, there is the fear that the ink may be transferred from the pitch roller to a sheet of printing paper.
The problem of the ink deposition on the wiping means can be solved by installing a wiper cleaner for cleaning the wiping means in place. It means that the wiper cleaner keeps the wiping means clean at all times.
However, we should take another measures against the problem that the ink is deposited on the portion of the face of the printing head where the wiping member cannot contact with. Viscous ink may be deposited on a particular place of the face which cannot be contact with the wiping member unless the relative position between the printing head and the wiping means is changed. Therefore, there is the idea that the relative position between the printing head and the wiping means is delicately displaced at the time the wiping operation begin to start to decrease the deposition of viscous ink deposition even in small quantities. Furthermore, an additional wiping means which is broader than the printing head may be installed to prevent the deposition of viscous ink on the face. However, there is no fundamental solution of the problem of depositing ink on the edge of the face.
Each of FIGS. 29 and 30 illustrates an inkjet printing head and a carriage for explaining the problem of depositing ink on the edge of the face in the printing head.
In inkjet printing heads H (111, 112) to be mounted on a carriage C, as shown in FIG. 29, an electric contact portion 23 having contacts 22 to receive driving signals for the printing head is provided on the upper portion of the side of the printing head 21. On the other hand, a carriage C has insertion portions for receiving the printing heads H (111, 112). These insertion portions have their respective electric contact portions 24, 25 with contact points 22A, respectively. The contact point 22A is responsible for transmitting a signal to the printing head H by contacting with the electric contact portion 23 on the head""s side. In addition, the electric contact portions 24, 25 establish connection with a control system on a main body of the printing apparatus. As shown in FIG. 29, the printing head H can be placed in the carriage C through an opening in the direction shown by the arrow. It is noted that an ink deposit I can be found on the side of the head H because the wiping means pushes the ink deposit I aside at the time of cleaning operation.
When the printing head H with the ink deposit I is inserted in the carriage C or withdrawn from the carriage C, there is a possibility that the ink deposition I on the side 21 of the head H comes in contact with the electric contact portions 24, 25 of the carriage C. A short circuit happens when the ink deposit I comes in contact with at least one of the electric contact portions 24, 25 increasing the risk of damage to the control system of the body.
An object of the present invention is to provide a cleaning device and a cleaning method for an inkjet head, a wiper used in such device and method, and an inkjet printing apparatus.
In the first aspect of the present invention, there is provided a cleaning device for an ink-jet printing head having an ink-ejecting surface where a plurality of ink-ejecting ports is formed for ejecting ink, in which the ink-ejection surface is cleaned by a relative movement between the printing head and the cleaning device, the cleaning device comprising:
a deposit-removing member facing to a side of the printing head, where
the side of the printing head extends substantially in the direction along a relative movement between the printing head and the cleaning means and positioned along an edge of the ink-ejecting surface.
In the second aspect of the present invention, there is provided a method of cleaning an ink-ejecting surface of a printing head by utilizing a relative movement with the printing head having the ink-ejecting surface where a plurality of ink-ejecting ports is formed for ejecting ink, comprising a step of:
cleaning the ink-ejecting surface of the printing head, concurrently with removing a deposit on a side of the printing head, where the side is located along an edge of the ink-ejecting surface.
In the third aspect of the present invention, there is provided an inkjet printing apparatus that forms an image on a printing medium using a printing head having an ink-ejecting surface where a plurality of ink-ejecting ports is formed for ejecting ink, comprising:
a deposit-removing member which is able to perform a relative movement with a side of the printing head, where
the side of the printing head is positioned along an edge of the ink-ejecting surface.
In the fourth aspect of the present invention, there is provided a wiper provided in an inkjet printing apparatus using an ink-jet printing head having an ink-ejecting surface where a plurality of ink-ejecting ports is formed for ejecting ink, comprising:
a deposit-removing member which is able to perform a relative movement with a side of the printing head, where
the side of the printing head is positioned along an edge of the ink-ejecting surface.
According to the present invention, the side of an inkjet printing head can be wiped to prevent an ink deposition caused by an increase in the viscosity of ink. As a result, there is no possibility of making a sheet of printing paper dirty.
A wiping operation for the side of the head according to the present invention includes: the relative movement of an elastic member keeping contact with the side of the head; and the relative movement of the elastic member at a location some distance from the side of the printing head in order to remove the ink deposit. Regarding the latter, we refer the relative movement as one having the spacing or clearance between the two. In addition, it is noted that a wiping for an orifice surface of the printing head is the type of performing a sliding-contact cleaning.
Furthermore, the present invention makes an inkjet printing apparatus as compact as possible with the ability of preventing a deposition of viscous ink by providing a scraper which is able to protrude to the side of the printing head and performs the relative movement against the printing head. Consequently, there is no possibility to dirty the printing medium, the exterior, and the user""s hand, and also there is no possibility to produce the adverse effect (e.g., less or no continuity of signal lines as a result of making an electric contact surface of the head) on the operating characteristics of the printing head.
The scraper protrudes to the side of the head by the motion of a capping member that performs the relative movement against the printing head, so that there is no need to install an extra mechanism for operating the scraper. Therefore, it is possible to simplify the configuration.
In addition, there is no need to provide an additional part as a result of providing the scraper as a part of the capping member that performs the relative movement against the printing head.
It is possible to prevent the accumulation of viscous ink by appropriately keeping the scraper in slide-contact with the side of the printing head as a result of providing the scraper as an elastic member.
A printing quality can be improved by appropriately ejecting ink as a result that the printing head includes electro-thermal conversion elements that generate thermal energies for ejecting ink from the corresponding orifices.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings